Flat glass sight gauge

ABSTRACT

The invention provides a flat glass sight gauge which may have a length ranging up to 4 meters or more and in which a plurality of sight glasses (10) are aligned end to end to give the required length, the glasses being bolted to a frontal face of a structurally stiff metal backing plate (13), the fluid connections required between the aligned glasses (10) being formed at the rear of the backing plate (13), by rigid metal connector blocks (16) which serve also to give structural reinforcement to the backing plate (13) at the ends of the sight glasses (10). This proposal allows for efficient sealing of all the liquid passages of the gauge and for structural integrity of the gauge assembly, enabling it to withstand rough handling, vibration and severe changes of pressure and temperature.

This invention relates to liquid level gauges incorporating aligned flatsight glasses.

Flat glass sight gauges are known, in which a heavy pressed safety glasswith a grooved or fluted face on the liquid side is clamped withintervening seals or gaskets between a metal windowed plate and a metalbase plate. The base plate may define in part, a passage in which theliquid, whose level is to be viewed, rises and falls. The grooved orfluted face of the glass which is in contact with the liquid provides anoptical effect, whereby the appearance of the glass is silvery in thespace above the liquid, but black where liquid is present. This contrastis very helpful in rendering visible the level of even colourlessliquids.

In the past flat glass gauges have been either of such a weak structuraldesign that they have been prone to breakage or leakage, or, they havebeen excessively heavy and cumbersome in construction, and it is onepurpose of the present invention to provide a gauge construction withgood strength/weight characteristics and which still offers the fullsafety which is normally expected from these gauges, against breakageand leakage under pressure, vibration, rough handling and severe changesof temperature.

It is a purpose of this invention to provide a gauge, which is of boltedup kit construction, which is easy to install without need for anyvulnerable weld or braze joints which are often difficult and costly toproduce and in particular, whose length may vary. The length of thegauge can range up to 4 meters or more, and the scope of application ofthe gauge construction, as now envisaged, is for measuring, by sight,the levels in containers, of fuels, oils and non viscous liquids up to,say, 1500 secs. Redwood, whether stored in atmospheric tanks andreservoirs or in tanks under pressure of up to say, 5 bar.

Broadly, the invention provides a flat glass sight gauge in which aplurality of sight glasses are aligned end to end to give the requiredlength, the glasses being bolted to a frontal face of a structurallystiff metal backing plate, the fluid connections required between thealigned glasses being formed at the rear of the backing plate, by rigidmetal connector blocks which serve also to give structural reinforcementto the backing plate at the ends of the sight glasses.

As will be seen this proposal allows for efficient sealing of all theliquid passages of the gauge and for structural integrity of the gaugeassembly, enabling it to withstand rough handling, vibration and severechanges of pressure and temperature.

A particular advantage which is achieved by the construction nowproposed, is that efficient sealing may be accomplished by interposingsealing strips or gaskets between surfaces which are planar andcontinuous over the whole area of each seal. This sealing efficiency isobtainable firstly, in the case of the seal between the flat sightglasses and the backing plate, which seals can completely surround themouth of a liquid receiving trough in each glass,; and secondly, in thecase of sealing gaskets interposed between the backing plate on itsreverse side, and the connector blocks. These flat surfaces can be madeto bring pressure evenly on to the whole area of each seal, suitably byemploying the same bolts which are used to secure the glasses and theconnector blocks to the backing plate.

The invention affords a versatile sight gauge installation which mayhave a length ranging up to 4 meters or more. It utilizes a plurality offlat sight glasses aligned end to end. The structural integrity of theinstallation is provided mainly by the backing plate. Where two or morebacking plates are provided the rigid metal connector blocks bolted tothe rear of the backing plate, form a structural bridge between thealigned backing plates. At the same time, the connector blocks provideliquid inter-communication, with efficient sealing, between adjacentaligned glasses. A cover plate bolted to the backing plate contributesto the structural strength of the installation, the glasses themselvesbeing largely relieved of stress. This structural strength enables theinstallation to withstand vibration, rough handling and changes ofpressure and temperature. The versatility may be enhanced by C-clampsfor securing the installation to a tank wall, being adjustablelongitudinally of the backing plate; while provision for positionaladjustment of its end fittings is also provided for, as is the equippingof the gauge with the ability to have end fittings of any required typeattached to rigid end connector blocks or pipes leading therefrom.

Sight gauge constructions are known whereby the sight tubes terminate inbanjo-type couplings or unions which are fitted over cylindrical pipeshaving bores communicating with the interiors of liquid containers; orthe banjo-type couplings may be fitted over cylindrical parts of valvebodies, screwed into tank walls or into bosses formed on such walls ofcontainers or tanks. There are many installations of gauges in existencewith banjo-type couplings of the kind referred to, but fitted with roundglass tubes. It is one purpose of the present invention to allowconversion of gauge installations, from round to flat glass sight tubes,with an execution which will meet up to date Official requirements forflat glass gauges. Acordingly, it is a further intention that the gaugeproposed, should be capable of being equipped with one or more endfittings of the kind comprising banjo-type couplings, such as will fitover existing cylindrical tank fittings, which may be valve bodiesscrewed into suitable tank bosses.

The present invention provides according to one aspect, a flat glasssight gauge comprising at least two sighting glasses aligned end to endand each comprising an elongate glass block having a longitudinal troughformed in a major face thereof so as to be surrounded by a continuoussubstantially planar marginal portion of that face, which trough has abase provided with longitudinal prismatic grooves; an endless strip ofsealing material being disposed to extend around said trough and to forma seal between a said substantially planar marginal face portion of asaid sighting glass and a metal backing plate. Both means are providedfor clamping each said sighting glass to a said backing plate. The oreach said backing plate is apertured at or towards each end of each saidtrough and a rigid metal connector block is bolted to the reverse sideof the backing plate and sealed over the rear of each said aperture,said connector block having a duct giving sealed intercommunicationbetween adjacent ends of successive troughs intermediate the ends of thegauge, and, at the ends of the gauge, between the ends of the troughsand a respective gauge end fitting, said connector blocks serving alsoto provide structural reinforcement to the gauge in regions where theglass blocks terminate.

Said backing plate is preferably U or channel-shaped in cross-section,so as to to structurally stiff, and it may be longitudinallyco-extensive with at least two such glass blocks secured to its frontalface in end to end alignment; or, a plurality of backing plates may bearranged in end to end alignment, each backing plate having a singleglass block secured on its frontal face.

Preferably, the means providing intercommunication between the adjacentends of the troughs of two adjacent glass blocks, comprise metalconnector blocks secured on the reverse faces of the backing plate orplates, the connector blocks being formed with cavities and/or holes andpassages which will provide liquid interconnections between adjacentaligned glass blocks, while liquid tight seals are formed with the aidof sealing rings or gaskets bedding against said backing plate on itsreverse side, and against the connector blocks.

The metal connector blocks secured on the reverse sides of the backingplate or plates, may have holes aligning with holes in the backingplate, there being sealing rings surrounding the mouths of the holes inthe connector blocks and passage means in each connector block leadingbetween the holes in the block. Such a connecting block will be providedat each junction between adjacent aligned glass blocks.

Each glass block is preferably secured against the backing plate bybeing sandwiched between the backing plate and a cover plate, the coverplate being bolted to the backing plate and having lateral flanges whichbutt with the backing plate on tightening the bolts so as to limitexcessive transverse flexing of the backing plate.

Each said cover plate may be longitudinally co-extensive with at leasttwo glass blocks arranged end to end in alignment.

At least two sighting glasses are described above, together with meansfor providing liquid flow intercommunication between the troughs ofadjacent glasses are preferably combined in an installation. Such aninstallation will include adjustable clamping means for securing it tothe wall of a liquid container and means will be provided, preferably inthe form of a positionally adjustable end fitting to give liquid flowintercommunication between the tank interior and the trough in which theliquid rises and falls so that its level can be viewed through of theflat sight glasses.

According to this aspect of the invention, such an installationcomprises, in combination; at least two elongate rectangular blocks ofglass, each block having formed in one of its major faces a trough whichextends longitudinally of the major length of said face, but terminatesshort of the ends of the block, so as to leave a flat surface on thesaid major face of the block surrounding the mouth of the trough of eachglass block; the base of each trough being formed with a plurality oflongitudinally extending, parallel prismatic grooves; a metal backingchannel which is longitudinally extensive with at least one of saidglass blocks; an endless strip of sealing material being disposed onsaid flat surface surrounding the mouth of the trough; said strip beingsandwiched between the block and a flat frontal face of the backingchannel to which the block is clamped; the said backing channel beingapertured to provide holes leading to the opposite ends of the trough;and wherein the at least two such glass blocks are secured end to end inalignment and including means for providing liquid intercommunicationbetween the holes leading to adjacent ends of the two troughs of thesaid two adjacent blocks; said means comprising for each junctionbetween adjacent glass blocks, a metal connector block secured on thereverse face of the backing channel between lateral flanges of saidchannel which extend longitudinally over the full length thereof; theconnector block having a duct communicating between the holes in thebacking channel, each said hole communicating with an end of a saidtrough, and sealing means surrounding the mouths of the holes in theconnector block; the means securing the connector block to the reverseface of the backing channel consisting of bolts, which on beingtightened, also impose pressure on the seals.

Preferably, in such an intallation, the gauge is provided at one or bothof its ends with a banjo-type pipe coupling for providing liquid flowintercommunication between the adjacent end of a sight glass trough, andthe bore of a pipe communicating with the interior of a liquidcontainer, said trough and said pipe bore extending approximately atright angles to one another and said banjo-type coupling surroundingsaid bore, the distance between the banjo-type pipe coupling and thetrough being adjustable in the direction in which the trough extendslongitudinally.

At least one clamp may engage each backing channel with means foraffixing the clamp to a wall for mounting the gauge onto a liquidcontainer of which said wall forms a part. Said clamp may be a C-clampand will be adjustable longitudinally of the backing channel, prior tobeing or after having been fixed to the tank wall.

The connector blocks, in some cases, may form structural connectionsbetween adjacent backing plates which are aligned end to end.

The invention will be described, by way of example, with reference tothe accompanying drawings in which:

FIG. 1 is a perspective view, cut-away in part, of a flat glass sightgauge assembly.

FIG. 2 is a front view of the assembly shown in FIG. 1.

FIG. 3 is a cross-sectional view taken on the lines indicated atIII--III of FIG. 2.;

FIG. 4 is a cross-sectional view taken on the line IV--IV of FIG. 2.FIG. 4 also shows a connector block device of a first preferred type,for providing liquid flow intercommunication between liquid passages, oras they will be termed, troughs, of two sight glasses disposed end toend in alignment.

FIG. 5 is a plan view of a connector block of the type used in FIG. 4.

FIG. 6 is a cross-sectional view taken on the line VI--VI of FIG. 5.

FIG. 7 is a cross-sectional view of a second preferred type of connectorblock.

FIGS. 8 and 9 are plan and side views of a gasket used in sealing theconnector blocks of the type shown in FIGS. 7. and 10.

FIG. 10 shows a connector block of the same type depicted in FIG. 7, butshown when employed in a butt joint between two sight glasses and twobacking plates each disposed end to end.

FIGS. 11 to 14 are views of a component of the connector block used inFIGS. 7 and 10; FIG. 11 being a plan view; FIGS. 12 and 13 beingcross-sectional views, taken respectively, on the lines XII--XII andXIII--XIII shown in FIG. 11; while FIG. 14 is an under plan view.

FIG. 15 is a plan view of a sandwich plate employed between the sealinggaskets of the arrangment depicted in FIG. 10.

FIG. 16 is a view similar to the upper portion of FIG. 4, showing incross-section, an alternative upper end fitting for the gauge assembly.

Referring now to the drawings, and first in particular to FIGS. 1 to 4,a flat glass sight gauge comprises at least two sighting glasses 1a and1b, which are aligned end to end. Each sighting glass comprises anelongate glass block 10, having a longitudinal trough 15 (whose base isprovided with longitudinal prismatic grooves 11) formed in a major faceof the block so as to be surrounded by a continuous substantially planarmarginal portion 14 of that face of the block.

At least one endless strip 12 of sealing material, is disposed tosurround each trough 15 and to form a seal between the substantiallyplanar face portion 14 of each glass block 10 and a a frontal planarface of a metal backing plate 13. The backing plate 13 has lateralflanges 113 so that it is U-shaped as seen in FIG. 3; this U orchannel-shape gives the backing plate a configuration of greatstructural stiffness.

Clamping means, for clamping each said sighting glass to a said backingplate 13, comprise a cover plate 21 secured to the backing plate 13, onbolts 26 being tightened. Strips 22 of cushioning material areinterposed between the glass 10 and the cover plate 21. The cover plate21 has lateral flanges 23 which may abut with the backing plate 13; theflanges also prevent flexing of the plate 13 when the bolts 26 aretightened.

Thus the gauge assembly, when bolted up will be afforded structuralstiffnes and strength, by the channel configuration given to both thebacking plate 13 and to the cover plate 21.

Each cover plate 21 may be co-extensive with two glass blocks 10,disposed aligned end to end, and in the example shown in FIG. 1, thebacking plate 13 is also co-extensive with the two blocks 10 forming thesight glasses 1a and 1b. The cover plate 21 has oblong windows 27through which the glasses are exposed to view.

Each said backing plate 13 is apertured at or towards each end of thetrough 15 in each block 10, and conduit means in the form of connectorblocks generally designated 16, (see FIG. 4), are sealed over the rearof each said aperture so as to give sealed intercommunication betweenadjacent ends of successive troughs 15, intermediate the ends of thegauge. At the ends of the gauge, further connector blocks 16 areprovided to give sealed liquid flow intercommunication between the endsof the troughs 15 and two gauge end fittings, generally designated 17and 18.

The troughs 15 interconnected by the conduit means 16, form a closedpassage way, extending continuously between the end fittings 17 and 18.Liquid admitted through the end fitting 17, which will be disposed belowthe fitting 18 when the gauge is disposed for use, will enter thecontinuous passage way, and its level in the passage way can be detectedthrough the viewing windows 27 and through the glass blocks 10.

As will be seen, it is possible to arrange any required number of glassblocks 10 disposed end to end, and it is a feature of the design thatthe distance between the end fittings 17 and 18, is adjustable, withinlimits wide enough to allow convenient installation on existing, or onnew, bosses or tappings formed on or in the walls of a container, andwhich bosses or tappings may be positioned with their centres atrelatively wide tolerances.

This is achieved, for example, by the longitudinal adjustability of theclamping means to be described with reference to FIG. 3, and by thearrangement for longitudinal adjustability of the upper end fittingshown in FIG. 16, and which will be described below. First however, thelower end fitting will be described with particular reference to FIG. 4.

In FIG. 4, 100 represents the wall of a tank or container. A boss 101 iswelded at 102 to the tank wall 100, and the boss has a through bore 103,which will communicate through a hole in wall 100 (not shown) with theinterior of the tank. 10 indicates a glass block of a sight gauge andthe block 10 defines a trough 15 extending over a frontal face of thebacking plate 13. Adjacent the end of the trough 15 the backing plate isapertured at 130. Bolted to the rear of the backing plate 13 is aconnector block 131 which contains a passage 132 which communicates withthe hole 130 and with the trough 15. 133 is a seal at the mouth of thehole 130. The block 131 has a banjo-type extension 134 (see also FIGS. 1and 2) which fits over a cylindrical extension 107 of the boss 101. Thiscylindrical extension 107 defines the bore 103 and has also radial bores108 which provide communication between the bore 103 and the passage 132in the connector block 131. The extension 107 of the boss (which may bean existing valve or like fitting provided on the wall of a tank orcontainer) is threaded to receive nuts 139 and 140 for clamping thebanjo-type extension 134 of the connector block 131. 109 generallyrepresents a tap screw which may be employed to drain the contents ofthe sight guage.

The upper end fitting 18 in FIG. 4, comprises a connector block 231bolted to the rear face of backing plate 13, and having a passage 232communicating with the trough 15 through a hole 230 in the backing plate13. A pipe 234 is secured by a gland nut 235 to a fitting 236 threadedlysecured to the block 231. 233 is a seal at the mouth of the hole 230 inthe backing plate 13, the seal being seated in a recess formed for thepurpose in the connector block 231.

The upper end fitting in FIG. 16 is somewhat similar to that shown inFIG. 4, except that the pipe 234 is adjustable longitudinally relativeto the connector block 231, such adjustability being permitted by agland nut 235 which in this case is threaded to a tapped hole in theblock 231 to urge a seal ring 237 backed up by a washer 239 to sealbetween the pipe and the block 231 which has a frusto-conically taperingbore in this region. The pipe 234 leads to a banjo extension 334 whichsurrounds a spigot 336. The spigot 336 is cylindrical and forms part ofa hollow plug 337 which is threaded in a boss 401 secured by welds 402to a tank wall 100. The spigot 336 has an axial bore 403 and radialbores 408, which communicate with the bore of the pipe 234.

The adjustability of the pipe 234 relative to the block 231, willprovide accommodation for variations, within predetermined limits, ofthe pre-established distances between the locations on the tank wall100, for the bottom fitting 17 and for the upper fitting 18 of FIG. 16.Further variation in the distance between such upper and lowerlocations, already established in the case of existing tanks, will beaccommodated by including in the gauge installation, an appropriatenumber of sighting glasses 1a, 1b, each of an appropriate length andarranged end to end; these will be provided with intercommunicatingmeans for their respective troughs as will be described below, firstwith reference to FIGS. 4 to 6, alternative intercommunicating meansbeing shown in FIGS. 7 to 15.

Referring to FIGS. 1 to 4, the end fittings 17 and 18 may be seen andunderstood to provide means for securing the ends of the guage assemblyto the tank wall 100. At intermediate regions of its length the guagewill be secured by the clamping arrangement depicted in FIG. 3. In FIG.3, 10 again represents the sight glass, and 21 its windowed cover plate,secured by bolts 26 to the backing plate 13, 12 and 22 being interposedsealing strips. 23 again designates the lateral flanges of the coverplate 21 which butt with the backing plate 13 to limit flexing of thelatter. The backing plate 13 itself has lateral flanges 113 which affordit structural stiffness. 114 represents a C-clip secured by bolts 115 toa boss 116, welded to the wall 100 of the tank. The C-clip 114 embracesthe flanges 113 of the backing plate 13, and is tightened by means of aclamping screw 117 having a nut 118.

In FIG. 2, such a clamping arrangement is designated generally at 120and any number of clamps 120 may be provided, as necessary, over thelength of the guage, such as will locate it securely on the tank wall.Such clamps will be adjustable longitudinally of the backing plate sothat they may be located appropriately to be bolted to pre positionedbosses 116 welded to the wall 100. Alternatively in another installationthe clamps might be affixed to threaded sockets by fixing bolts, suchsockets already existing in the wall 100, and the clamps may need to beappropriately adjusted to suit the locations of these sockets. In thecase of a new installation an appropriate number of evenly spaced bosses116 may be welded in position; or threaded sockets may be provided forreceiving bolts 115.

Reference will now be made to FIGS. 4, 5 and 6. In FIG. 4, two sightglasses 1a and 1b are shown aligned with their ends nearly abutting.Each comprises a glass block 10 defining, with a backing plate 13, atrough 15. At the junction between the two glasses 10, means have to beprovided for interconnecting the adjacent ends of the two troughs 15. Inthe embodiment of FIGS. 4 to 6, these interconnecting means comprise theconnector block 431, shown in FIGS. 5 and 6, secured by bolts 260 to thereverse face of the backing plate 13 between its lateral flanges 113.

The backing plate 13 has through holes 130 opening into the troughs 15.The connector block 431 has one longitudinal bore 432 and two transversebores 433, the latter being positioned to align with the holes 130, andhaving enlarged mouth cavities 434 to receive O-rings 435 for sealingwith the backing plate 13 about the mouths of its holes 130. Thelongitudinal bore is closed at one end by a plug 436 its other end beingblind. The block 431 has tapped holes to receive the ends of bolts 26and 260, whereby it is secured on the reverse side of the backing plate13.

Instead of the O-rings 435, there could be employed a gasket as will bedescribed below with reference to FIGS. 7 to 15, such a gasket beingshown in FIGS. 8 and 9, in which case the cavities 434 might also beomitted.

A different design of connector block 731 is shown in FIGS. 11 to 14.This is employed in the arrangements of intercommunicating means shownin FIGS. 7 and 10.

In FIGS. 7 and 10 two glass blocks 10 are aligned end to end, eachhaving a trough 15. In the case of FIG. 10 each glass block 10 has itsown backing plate, while FIG. 7 illustrates a junction in the case of abacking plate and a cover plate which are co-extensive with two glassblocks 10.

In the arrangement shown in FIG. 7, a single gasket 710 of the typeshown in FIGS. 8 and 9 is sandwiched between the connector block 731 andthe backing plate 13.

In FIG. 10 however there is a butt joint between two backing plates 13.Accordingly it is necessary to employ one gasket 710 against the backingplates 13 and a second gasket against the connector block 731. A plate715, (shown in FIG. 15) is sandwiched between the two gaskets 710. Thegaskets 710, the sandwich plate 715, and the connector block 731 are allapertured to allow passage to the stems of bolts 26 and 260.

Nuts are shown threaded on these bolts in these arrangements asillustrated; however the bolts could engage tapped holes in theconnector block 731.

The gasket 710 shown in FIGS. 8 and 9, has a main body position 718 ofplanar configuration preformed with holes 711 to allow passage to thebolts as described. It also has two through holes at 750 which arecalculated to align with holes 130 of the plate or plates 13 leading tothe adjacent ends of aligned troughs 15 in the glass blocks 10. Aroundthe holes 750, the gasket has preformed upstanding annular beads 751;also upstanding are bead portions 752 which, with the beads 751, have anoval configuration in plan view.

In the case of the sandwich gasket construction of FIG. 10, the annularbeads of the upper gasket, seal about the mouths of the holes 130 in thebacking plates 13, while the oval bead of the lower gasket, seals aboutthe mouth of an oval trough 716 of the connector block as best shown inFIG. 11. Finally, the gasket 710 may have short bead portions 712adjacent its bolt holes 711.

The sandwich plate 715, of FIG. 15, has holes for the bolts and twoholes 753 to align with the holes 750 of the gaskets 710.

The sandwich plate 715 is suitably of stainless steel, as arepreferably, each connector block, each cover plate 21 and each backingplate 13.

It will be noted in FIG. 10 that not only is each backing plate 13co-extensive with each glass block 10, but so also is each windowedcover plate 21. Thus in this embodiment the bolts 26 secure each block10 to form a unit with its own backing plate 13 and cover plate 21; thebolts 260 being to secure the extreme ends of the abutting units and toprovide an even distribution of pressure upon the whole extent of theseals 12 surrounding each trough and upon the gasket 710 whose bead 75lsurrounds the trough 716 in the connector block 731. It will also benoted that the connector block 731, secured by the bolts 26 and 260forms the sole structural connection between the two flat glass unitsaligned end to end, as shown in FIG. 10.

The invention provides significant improvements in flat glass sightgauges. A gauge installation may be shipped complete and fullyassembled; or it may be provided as a kit of parts which are easilyassembled on site. The clamping means provided are adjustablelongitudinally of the gauge assembly. The end fittings are adjustable tosuit the predetermined dimensions of a pre-existing installation so thata new gauge can be fitted instead of an existing one.

Although a particular type of end fitting has been described andillustrated, those skilled in the art will appreciate that other typesof end fitting, conventional in the art, could be used instead; forexample those incorporating bleed taps or valves.

The glasses and the channel members between which individual glasses arelocated, can be produced in sets each of different lengths, so that,with various lengths suitably combined, a wide range of overall lengthscan be achieved.

Replacement is easily accomplished by unskilled labour, on site.Leakages can be easily spotted and rectified by tightening or replacingseals.

The U or channel shaping of the backing plates provides the maincontribution to the structural stiffness and strength of theinstallation, while the metal connector blocks, which are securelybolted to the backing plates, may be employed to form structurallystrong connections between adjacent backing plates disposed aligned endto end. With this arrangment the glasses themselves are mainly relievedof structural stresses, as are also the C-clamps which merely secure thegauge installation of the wall of the tank or container.

The gauge now proposed will be found to have a strength/weightcharacteristic favourably comparable with that of any other gauge ofequivalent versatility.

We claim:
 1. A flat glass sight gauge in which a plurality of sightglasses are aligned end to end to give the required length, said gaugeincluding, in combination:at least two elongate rectangular blocks ofglass, each block having formed in one of its major faces a trough witha mouth which extends longitudinally of the major length of said face,but terminates short of the end of the block, so as to leave a flatsurface on the said major face of the block surrounding the mouth of thetrough of each glass block; the base of each trough being formed with aplurality of longitudinally extending, parallel prismatic grooves; metalbacking plate means for mounting said glass blocks, said backing platemeans having a flat frontal face and a reverse face with full lengthlaterally spaced flanges; an endless strip of sealing material beingdisposed on said flat surface surrounding the mouth of each trough; saidstrip being sandwiched between the block and the flat frontal face ofthe backing plate means to which the block is clamped; the said backingplate means being apertured to provide holes leading to the oppositeends of the troughs; and wherein at least two adjacent blocks aresecured end to end in alignment and including means for providing liquidintercommunication between the holes leading to adjacent ends of the twotroughs of the said two adjacent blocks; said means for providing liquidintercommunication comprising, for each junction between adjacent glassblocks, a metal connector block secured on and separable from thereverse face of the backing plate means between the lateral flanges ofsaid plate means; the connector block having a duct communicationbetween the holes in the backing plate means, each said holecommunicating with an end of a said trough, and sealing means in theconnector block surrounding the mouths of said holes; and bolts securingthe connector block to the reverse face of the backing plate means,which on being tightened, also impose pressure on the seals.
 2. A gaugeaccording to claim 1, wherein the gauge is provided at one or both ofits ends with a banjo-type pipe coupling for providing liquid flowintercommunication between an end trough of a sight glass, and the boreof a pipe communicating with the interior of a liquid container, saidend trough and said pipe bore extending approximately at right angles toone another, and said banjo-type coupling surrounding said bore, thedistance between the banjo-type pipe coupling and the end trough beingadjustable in the direction in which the end trough extendslongitudinally.
 3. A gauge according to claim 1, including at least oneclamp engaging said backing plate means, and means for affixing theclamp to a wall for mounting the gauge onto a liquid container of whichsaid wall forms a part, said clamp being a C-clamp and being adjustablelongitudinally of said backing plate means.
 4. A flat glass sight gaugein which a plurality of sight glasses are aligned end to end to give therequired length, said gauge comprising at least two sighting glassesaligned end to end and each comprising an elongate glass block having alongitudinal trough formed in a major face thereof so as to besurrounded by a continuous substantially planar marginal portion of thatface, which trough has a base provided with longitudinal prismaticgrooves;structural stiff metal backing plate means for mounting saidglass blocks; at least one endless strip of sealing material beingdisposed to surround each trough and to form a seal between a saidsubstantially planar marginal face portion of a said glass block andsaid metal backing plate means; bolt means for clamping each said glassblock to said backing plate means; said backing plate means havingapertures therethrough at or towards each end of each said trough andrigid metal connector blocks being bolted to the reverse side of thebacking plate means and sealed over the rear of each said aperture; saidconnector blocks having ducts forming a sealed conduit providing liquidintercommunication through the apertures and between adjacent ends ofsuccessive troughs intermediate the ends of the gauge, and, at the endsof the gauge, between the ends of the troughs and a respective gauge endfitting; liquid tight sealing means interposed between the connectorblocks and the backing plate means and sealing around the said aperturesin the backing plate means, said sealing means comprising an aperturedmetal plate sandwiched between two gaskets, one of the gaskets beddingagainst the reverse side of such backing plate means and the otherbedding against a planar face of a connector block; said connectorblocks serving also to provide structural reinforcement to the gauge inregions where the glass blocks terminate.
 5. A flat glass sight gauge inwhich a plurality of sight glasses are aligned end to end to give therequired length, said gauge comprising at least two sighting glassesaligned end to end and each comprising an elongate glass block having alongitudinal trough formed in a major face thereof so as to besurrounded by a continuous substantially planar marginal portion of thatface, which trough has a base provided with longitudinal prismaticgrooves;structurally stiff metal backing plate means for mounting saidglass blocks; at least one endless strip of sealing material beingdisposed to surround each trough and to form a seal between a saidsubstantially planar marginal face portion of a said glass block andsaid metal backing plate means; cover plate means for covering saidglass blocks; each glass block being secured against the backing platemeans by being sandwiched between the backing plate means and said coverplate means; bolt means for bolting said cover plate means to saidbacking plate means and clamping each said glass block to said backingplate means, both the backing plate means and the cover plate meanshaving lateral stiffening flanges to resist transverse flexing of theplate means when the bolt means is tightened; said backing plate meansbeing apertured at or towards each end of each said trough and rigidmetal connector blocks being bolted to the reverse side of the backingplate means and sealed over the rear of each said aperture; saidconnector blocks having ducts providing sealed intercommunicationbetween adjacent ends of successive troughs intermediate the ends of thegauge, and, at the ends of the gauge, between the ends of the troughsand a respective gauge end fitting; said connector blocks serving alsoto provide structural reinforcement to the gauge in regions where theglass blocks terminate.
 6. A gauge according to claim 5, wherein saidcover plate means comprises a cover plate for each glass block, eachsaid cover plate being windowed and longitudinally coextensive with onlyone glass block, structural support for two adjacent glass blocks,arranged end to end in alignment, being provided by said backing platemeans to which the two adjacent blocks, each with its cover plate, arebolted.
 7. A flat glass sight gauge in which a plurality of sightglasses are aligned end to end to give the required length, astructurally stiff metal base plate having a frontal face and a reverseside, the glasses being secured to the frontal face of said structurallystiff metal base plate and defining fluid passages at the front of thebase plate visible through the aligned glasses, fluid connectionsbetween the aligned glasses being formed at the reverse side of the baseplate, rigid metal connector block means overlying the aligned ends ofthe sight glasses and being secured by screwthreaded bolt means to thereverse side of the base plate, said fluid connections being defined byapertures in said base plate and passages in said connector block means,cover plate means for covering said sight glasses, each glass beingsandwiched between the base plate and said cover plate means, said coverplate means being secured by said screwthreaded bolt means to the baseplate, and wherein the base plate and the cover plate means have lateralstiffening flanges so as to resist transverse flexing when thescrewthreaded bolt means are tightened, said cover plate means beingwindowed to permit viewing of the fluid passages defined by the sightglasses.
 8. A sight gauge according to claim 7, including liquid tightsealing means interposed between said connector block means and thereverse side of the base plate, said sealing means sealing around saidapertures in the said base plate, with said sealing means comprising anapertured metal plate sandwiched between two gaskets, one of the gasketsbedding against the reverse side of the base plate and the other beddingagainst a planar face of the said conenctor block means.
 9. A flat glasssight gauge comprising at least two sight glalsses aligned end to endand each comprising an elongate glass block having a longitudinal troughformed in a major face thereof so as to be surrounded by a continuoussubstantially planar marginal portion of that face, which trough has abase provided with longitudinal prismatic grooves;a metal base platehaving a frontal face; at least one endless strip of sealing materialbeing disposed to surround each trough and form a seal between thesubstantially planar marginal face portion thereof and said frontal faceof the metal base plate; said base plate having apertures at or towardseach end of each said trough and rigid metal connector block means forcommunicating said troughs, said connector block means being secured tothe reverse side of and separable from the base plate and sealed oversaid apertures; said metal connector block means having duct meansproviding, with said apertures, sealed intercommunication betweenadjacent ends of successive troughs intermediate the ends of the gauge,and, at the ends of the gauge, between the ends of the troughs and arespective gauge end fitting; cover plate means for covering said glassblocks; each glass block being secured against the frontal face of thebase plate by being sandwiched between the base plate and said coverplate means secured by screwthreaded bolt means to the base plate, saidbolt means securing said connector block means to the reverse side ofthe base plate; said base plate and said cover plate means have lateralstiffening flanges resisting transverse flexing of the plates when thescrewthreaded bolt means are tightened.
 10. A gauge according to claim9, including liquid tight sealing means interposed between saidconnector block means and the reverse side of the base plate for sealingaround said apertures in the said base plate, said sealing meanscomprising an apertured metal plate sandwiched between two gaskets, oneof the gaskets bedding against the reverse side of the base plate andthe other bedding against a planar face of said connector block means.11. A gauge according to claim 9, wherein said cover plate meanscomprises a single cover plate, said base plate and said cover platebeing coextensive, a plurality of glass blocks being secured betweensaid base plate and said cover plate.
 12. A gauge according to claim 9,wherein said base plate is longitudinally coextensive with at least twosuch glass blocks secured to its frontal face in end to end alignment.13. A gauge according to claim 12, wherein said cover plate meanscomprises plural cover plates, each said cover plate being windowed andlongitudinally coextensive with only one glass block.
 14. A gaugeaccording to claim 12, wherein said cover plate means is windowed andlongitudinally coextensive with at least two glass blocks.
 15. A flatglass sight gauge comprising at least two sight glasses aligned end toend and each comprising an elongate glass block having a longitudinaltrough formed in a major face thereof so as to be surrounded by acontinuous substantially planar marginal portion of that face, whichtrough has a base provided with longitudinal prismatic grooves; a metalbase plate and a windowed cover plate associated with each glass block,at least one endless strip of sealing material being disposed tosurround the said trough of each glass block and to form a seal betweenthe substantially planar marginal face portion of said sight glass blockand the associated metal base plate; each said base plate beingcoextensive with the associated sight glass block with the glass blockbeing sandwiched between the base plate and the associated windowedcover plate which is also coextensive with the glass block, the baseplates backing adjacent aligned glass blocks abutting end to end, andthe cover plates of said adjacent aligned glass blocks abutting end toend; and means providing sealed liquid flow intercommuniation betweenthe adjacent ends of the troughs of two adjacent aligned glass blocks,said means comprising a single metal connector block secured on andseparate from the reverse faces of the two abutting base platesrespectively backing the two glass blocks, apertures leading througheach of the two base plates to the troughs of the respective adjacentaligned glass blocks, the metal connector block including a conduit toprovide liquid interconnections between said apertures with liquid tightsealing means being interposed between the single connector block andthe two backing plates and sealing around the said apertures in the saidbacking plates, said sealing means comprising an apertured metal platesandwiched between two gaskets, one of the gaskets bedding against thereverse side of both said base plates and the other bedding against aplanar face of the said connector block.
 16. A sight gauge according toclaim 15, wherein each cover plate is a U-sectioned metal channel memberhaving flanges extending longitudinally over its full length, the glassblocks being located between the said cover plate flanges, and includingat the location of the junction between two adjacent aligned glassblocks, screw threaded fastening bolt means passing through said coverplates and said base plates of said respective glass blocks, and throughthe connector block at said location, said fastening bolt means on beingtightened, securing said cover plates, glass blocks, base plates andconnector block together, and exerting pressure on the interposed glassblocks with their associated seals, as well as on the seal means betweenthe connector block and the reverse sides of the base plates where theyabut end to end at that location, over-tigtening of said fastening meansbeing prevented by the lateral flanges of said cover plates abuttingagainst said base plates.